Generally, a reciprocating compressor serves to intake, compress, and discharge a refrigerant as a piston linearly reciprocates within a cylinder. The reciprocating compressor may be classified into a connection type reciprocating compressor or a vibration type reciprocating compressor according to the method employed to drive the piston.
In the connection type reciprocating compressor, the piston is connected to a rotating shaft associated with a rotation motor by a connection rod, which causes the piston to reciprocate within the cylinder, thereby compressing the refrigerant. On the other hand, in the vibration type reciprocating compressor, the piston is connected to a mover associated with a reciprocating motor, which vibrates the piston while the piston reciprocates within the cylinder, thereby compressing the refrigerant. The present invention relates to the vibration type reciprocating compressor, and the term “reciprocating compressor” will hereinafter refer to the vibration type reciprocating compressor.
To enhance the performance of a reciprocating compressor, a portion between the cylinder and the piston, being hermetically sealed, has to be properly lubricated. To this end, there has been conventionally known a reciprocating compressor which seals and lubricates the portion between the cylinder and the piston by supplying a lubricant such as oil between the cylinder and the piston and forming an oil film. However, the supplying of the lubricant requires an oil supply apparatus, and an oil shortage may occur depending on operation conditions, thereby degrading compressor performance. Also, the compressor size needs to be increased because a space for receiving a certain amount of oil is required, and the installation direction of the compressor is limited because the entrance of the oil supply apparatus should always be kept immersed in oil.
Taking into consideration the disadvantages of the oil-lubricated type reciprocating compressor, as illustrated in FIGS. 1 and 2, there has been conventionally known a technique of forming a fluid bearing between a piston 1 and a cylinder 2 by bypassing a part of compressed gas between the piston 1 and the cylinder 2. A plurality of gas holes 2a each having a small diameter are formed through the cylinder 2 to inject the compression gas into an inner circumferential surface of the cylinder 2.
This technique can simplify a lubrication structure of the compressor because it requires no oil supply apparatus, unlike the oil-lubricated type for supplying oil between the piston 1 and the cylinder 2, and can maintain constant compressor performance by preventing an oil shortage depending on operating conditions. Also, this technique has the advantage that the compressor can be smaller in size and the installation direction of the compressor can be freely designed because no space for receiving oil is required in the casing of the compressor. Unexplained reference number 3 denotes a plate spring (a leaf spring), 5a to 5c denote connecting bars, and 6a and 6b denote links.
However, in the related art reciprocating compressor, foreign substances mixed with refrigerant gas are introduced into the a fluid bearing to block the fluid bearing, thereby preventing the refrigerant gas from being supplied between the cylinder 2 and the piston 1. Accordingly, concentricity between the piston 1 and the cylinder 2 is destroyed, thereby causing a friction loss and abrasion while the piston 1 reciprocates with being closely adhered to the cylinder 2.
Also, as high-temperature refrigerant gas discharged from a compression space is introduced into the fluid bearing to heat the cylinder 2, a specific volume of a compression space increases and thereby a suction loss is caused.
Furthermore, discharge noise and vibration which are generated while a refrigerant compressed in the compression space is discharged cannot effectively be offset, thereby increasing vibration noise of the compressor.